2006 Accord no heat

Joined
May 19, 2004
Messages
1,716
Location
Germantown, MD
Yesterday I did a drain and fill of my 2006 Accord sedan's coolant. It's an EX with leather, 4 cylinder, stick shift.

After the fill I had the engine running, it got up to temp, fans on, and then I switched the HVAC to Hi heat. No heat. Cold air out all the vents regardless of temperature setting, what vents selected, driver passenger side mix. I haven't run the heat since last winter when it worked fine.

The car gets up to temperature fine and the thermostat behaves as expected. I did a bit of research and found some info on the heater control valve, which is the valve that opens the flow to the heater core. This is opened and closed by a wire that I gather is actuated by something under the dash, perhaps the blend door motor?

Speaking of that blend door motor, I replaced it last spring as it was doing the back and forth hunting with grinding sounds. It fixed that problem but I do occasionally still get the behavior where it'll blend in more hot or ambient air that it should for a given temperature. I can "solve" this by setting the temperature low and slowing bringing it back up. I dunno if all of this is related
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I cycled the temp from Lo to Hi and noted that the cable doesn't move and thus neither does the heater valve. It is stuck at about 10:30, which I gather is half open half closed? I tried moving it either way with my fingers but could not get it to move with moderate force. Likewise the cable is on there pretty good and wouldn't come off with a moderate tug.

Any ideas?

jeff

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Does it have a slide lever for hot/cold, or is it electronic? Unfortunately my experience is with older Civics ('89, '90, nephew's '97), it was mechanical. If it's electrical, maybe the motor moving it has gotten stuck?
 
Compare the temp of the hose.... going in and going out of the HCV. If after getting the vehicle up to temp and the hose going from the HCV to the heater core is cold you may have a bad HCV.
 
Clean the grime off the valve, especially where the cable connects so you can get a better look at it. I can't tell for sure from the pic but it looks like the valve lever has a stud so maybe the cable slips onto that from the end (and might be easier to get off if the cable sheath is taken out of its mounting bracket a few inches away in the pic), or is there a hole or groove and a lock nut?

Get the cable off and see if it then moves, and if the valve moves by hand.

One or the other seems seized and if it's the valve you probably need to remove and replace or attempt to clean it. If the cable you need to figure out if the other end is actuating since it looks good on this end.
 
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That is the fully closed position. Do what Chris142 said. If the hot/cold control does something (due to the blend door), the other end of the cable is probably not attached or attached wrong after your motor replacement.

Once you get the valve open you will probably need to top up the radiator since there's air in the heater core that didn't come out yet.
 
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Thanks everybody. I didn't have much time for it yesterday so just fired some WD-40 on it to clear the grime, yet the cable didn't want to come off without tools. At some point in the next couple of days I'll get it off and see if I can move the valve manually and if the cable moves in response to the temperate setting.

jeff
 
Update - 20-25 minutes in to my 30 minute commute this morning I noticed some warmth coming through the vents (the temp was set to 70 and it was 70 outside), cranked it up and voila, hot air. Lowered it down and got cold out of both, raised it back up and hot again. I'll test it out again on the way home and check under the hood when the sun is out.

jeff
 
Well the problem either magically solved itself, or the WD40 loosened some gunk that had it stuck, because the valve appears to be working correctly now. Popped the hood this afternoon and had the kids cycle the temp from Lo to Hi and sure enough the cable was able to move it back and forth between the two positions in the photos.

The coolant is halfway between the Min and Max lines in the overflow tank when hot - I believe this is an OK level, or should I top it off to Max? If so should that be done hot or cold or does it matter? Thanks everybody,

jeff

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Don't just check in the tank. Park on level ground or facing uphill (that is you don't want it facing downhill, that way the radiator will be the highest point) and wait until completely cold. Then open the radiator-- if it is not all the way full top it up.
 
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Last update, I think
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I checked the level via the radiator fill and found that it did require another 1/3 of a gallon or so. Weird because the drain took just under a gallon out, and the fill took about 1.4 gallons
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Anyway that extra bit definitely affected how quickly heat became available, as it was blowing warm in just a couple of minutes rather than the 10+ observed in the previous few drives. Thanks everybody.

jeff
 
Well this problem has reared it's head again. I got away with it for 3 years lol.

I re-checked the heater control valve and it still moves correctly via the cable in response to adjusting the temperature from Lo to Hi. Next step is checking the coolant tomorrow morning.

jeff
 
I don’t think it’s common, but on my 03 accord (same body style) the blend door got stuck. Not just a bad actuator/blend door motor, but the actual door was stuck in place in the HVAC housing. I got a junkyard HVAC box. Worst repair that car needed, but it was a great car!
 
The car took about half a gallon of coolant this morning and now is behaving normally. Not sure where it's going but half a gallon in 3 years doesn't seem too bad lol.

jeff
 
Does it still have the original radiator? They tend to leak after several years. Look especially where the metal core joins the plastic at the top and bottom.
 
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